U.S. patent application number 13/310197 was filed with the patent office on 2012-03-29 for antenna module.
This patent application is currently assigned to MURATA MANUFACTURING CO., LTD.. Invention is credited to Kazunari KAWAHATA.
Application Number | 20120075158 13/310197 |
Document ID | / |
Family ID | 43297568 |
Filed Date | 2012-03-29 |
United States Patent
Application |
20120075158 |
Kind Code |
A1 |
KAWAHATA; Kazunari |
March 29, 2012 |
ANTENNA MODULE
Abstract
An antenna module is provided and includes two feeding parts and
having different frequencies of feeding on a circuit board. A first
feeding radiation electrode is connected to the feeding part on a
lower frequency side and performs an antenna operation. A second
feeding radiation electrode is connected to the feeding part on a
higher frequency side and performs an antenna operation. The first
and second feeding radiation electrodes electrically connected, and
the second feeding radiation electrode is smaller than and on the
first feeding radiation electrode with an insulating part
therebetween. The first feeding radiation electrode is configured
to serve as an electrode that also performs an antenna operation of
the second feeding radiation electrode, in such a manner that the
second feeding radiation electrode performs an antenna operation in
which the second feeding radiation electrode and the first feeding
radiation electrode are electrically coupled to each other.
Inventors: |
KAWAHATA; Kazunari;
(Kyoto-fu, JP) |
Assignee: |
MURATA MANUFACTURING CO.,
LTD.
Kyoto-fu
JP
|
Family ID: |
43297568 |
Appl. No.: |
13/310197 |
Filed: |
December 2, 2011 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP2010/056695 |
Apr 14, 2010 |
|
|
|
13310197 |
|
|
|
|
Current U.S.
Class: |
343/858 ;
343/893 |
Current CPC
Class: |
H01Q 5/40 20150115; H01Q
21/30 20130101; H01Q 9/285 20130101; H01Q 9/0421 20130101 |
Class at
Publication: |
343/858 ;
343/893 |
International
Class: |
H01Q 1/50 20060101
H01Q001/50; H01Q 21/28 20060101 H01Q021/28 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 3, 2009 |
JP |
2009-134228 |
Claims
1. An antenna module comprising: a circuit board including two
feeding parts having different frequencies of feeding on a first
frequency side and a second frequency side higher than the first
frequency side, respectively; a first feeding radiation electrode
connected to the feeding part on the lower frequency side and
performing an antenna operation; a second feeding radiation
electrode connected to the feeding part on a higher frequency side
and performing an antenna operation, said second feeding radiation
electrode is smaller than the first feeding radiation electrode,
formed on the first feeding radiation electrode with an insulating
part therebetween, and has an integrated structure with the first
feeding radiation electrode; and unbalanced feeding lines including
a hot line and a ground line connected to each of the first and
second feeding radiation electrodes, wherein each hot line is
connected to a corresponding one of the feeding parts, and the
ground line connected to the second feeding radiation electrode is
connected, via the first feeding radiation electrode, to a ground
provided on a side of the circuit board, in such a manner that the
second feeding radiation electrode performs an antenna operation in
which the second feeding radiation electrode and the first feeding
radiation electrode are electrically coupled to each other.
2. The antenna module according to claim 1, further comprising: a
circuit having a frequency characteristic exhibiting a high
impedance at an exciting frequency of the second feeding radiation
electrode connected to the ground line connected to the first
feeding radiation electrode; and a circuit having a frequency
characteristic exhibiting a high impedance at an exciting frequency
of the first feeding radiation electrode connected to the ground
line connected to the second feeding radiation electrode.
3. The antenna module according to claim 2, wherein, the ground
line connected to the second feeding radiation electrode is on the
same plane as the first feeding radiation electrode, and the hot
line connected to the second feeding radiation electrode is near
and forms a coplanar structure with the ground line.
4. The antenna module according to claim 2, wherein, the ground
line connected to the second feeding radiation electrode is formed
by employing the first feeding radiation electrode, and the hot
line is formed at a rear side of the ground line to provide a
microstrip line structure or a triplate structure.
5. The antenna module according to claim 1, further comprising: a
chip antenna including the second feeding radiation electrode on
the first feeding radiation electrode, wherein one end of the
second feeding radiation electrode is connected in a high-frequency
manner to the first feeding radiation electrode, such that the chip
antenna serves as a chip antenna of a .lamda./4-resonant type.
6. The antenna module according to claim 2, further comprising: a
chip antenna including the second feeding radiation electrode on
the first feeding radiation electrode, wherein one end of the
second feeding radiation electrode is connected in a high-frequency
manner to the first feeding radiation electrode, such that the chip
antenna serves as a chip antenna of a .lamda./4-resonant type.
7. The antenna module according to claim 3, further comprising: a
chip antenna including the second feeding radiation electrode on
the first feeding radiation electrode, wherein one end of the
second feeding radiation electrode is connected in a high-frequency
manner to the first feeding radiation electrode, such that the chip
antenna serves as a chip antenna of a .lamda./4-resonant type.
8. The antenna module according to claim 4, further comprising: a
chip antenna including the second feeding radiation electrode on
the first feeding radiation electrode, wherein one end of the
second feeding radiation electrode is connected in a high-frequency
manner to the first feeding radiation electrode, such that the chip
antenna serves as a chip antenna of a .lamda./4-resonant type.
9. The antenna module according to claim 5, wherein the second
feeding radiation electrode is formed of a helical electrode having
a helical structure, and the chip antenna including the second
feeding radiation electrode is provided on the first feeding
radiation electrode.
10. The antenna module according to claim 6, wherein the second
feeding radiation electrode is formed of a helical electrode having
a helical structure, and the chip antenna including the second
feeding radiation electrode is provided on the first feeding
radiation electrode.
11. The antenna module according to claim 7, wherein the second
feeding radiation electrode is formed of a helical electrode having
a helical structure, and the chip antenna including the second
feeding radiation electrode is provided on the first feeding
radiation electrode.
12. The antenna module according to claim 8, wherein the second
feeding radiation electrode is formed of a helical electrode having
a helical structure, and the chip antenna including the second
feeding radiation electrode is provided on the first feeding
radiation electrode.
13. The antenna module according to claim 2, wherein at least one
of the first and second feeding radiation electrodes is connected
to a frequency-variable circuit, and connection lines for
controlling the frequency-variable circuit are near the unbalanced
feeding lines.
14. The antenna module according to claim 3, wherein at least one
of the first and second feeding radiation electrodes is connected
to a frequency-variable circuit, and connection lines for
controlling the frequency-variable circuit are near the unbalanced
feeding lines.
15. The antenna module according to claim 4, wherein at least one
of the first and second feeding radiation electrodes is connected
to a frequency-variable circuit, and connection lines for
controlling the frequency-variable circuit are near the unbalanced
feeding lines.
16. The antenna module according to claim 1, wherein a matching
circuit is formed for at least the second feeding radiation
electrode, out of the second feeding radiation electrode and the
first feeding radiation electrode, and the matching circuit for the
second feeding radiation electrode is on the first feeding
radiation electrode.
17. The antenna module according to claim 2, wherein a matching
circuit is formed for at least the second feeding radiation
electrode, out of the second feeding radiation electrode and the
first feeding radiation electrode, and the matching circuit for the
second feeding radiation electrode is on the first feeding
radiation electrode.
18. The antenna module according to claim 3, wherein a matching
circuit is formed for at least the second feeding radiation
electrode, out of the second feeding radiation electrode and the
first feeding radiation electrode, and the matching circuit for the
second feeding radiation electrode is on the first feeding
radiation electrode.
19. The antenna module according to claim 4, wherein a matching
circuit is formed for at least the second feeding radiation
electrode, out of the second feeding radiation electrode and the
first feeding radiation electrode, and the matching circuit for the
second feeding radiation electrode is on the first feeding
radiation electrode.
20. The antenna module according to claim 1, wherein the first
feeding radiation electrode or the second feeding radiation
electrode is provided in a plural form.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation of International
Application No. PCT/JP2010/056695 filed Apr. 14, 2010, which claims
priority to Japanese Patent Application No. 2009-134228 filed Jun.
3, 2009, the entire contents of each of these applications being
incorporated herein by reference in their entirety.
TECHNICAL FIELD
[0002] The present invention relates to small-sized antenna modules
that can be applied to cellular phones, small-sized PCs, or the
like.
BACKGROUND
[0003] In recent years, multi-band antenna modules have been used
in wireless devices (e.g., cellular phones), and performance
improvement in such modules has been desired. FIG. 6 illustrates a
multi-band antenna structure of an example of related art applied
to a cellular phone. See, NTT Docomo Technical Journal Vol. 14, No.
2 (Non-Patent Document 1). In this antenna structure, an antenna
element 41 with a band of 800 MHz and an antenna element 42 with a
band of 1.7/2 GHz are individually formed. Radiation electrodes
forming the antenna elements 41 and 42 are connected to a switch 47
via feeding points 43 and 44 and matching circuits 45 and 46,
respectively, provided on the side of a casing 48, which is on the
side of keys. FIG. 6 illustrates an example of an antenna structure
provided in a foldable cellular phone. In the drawing, reference
numeral 49 denotes a casing on the side of a liquid crystal
display. In this structure, the antenna elements 41 and 42 each
perform a radiating operation including the casings 48 and 49.
[0004] FIG. 7 illustrates a multi-band antenna structure of another
example of related art. See, Japanese Unexamined Patent Application
Publication No. 2006-81181 (Patent Document 1). In this antenna
structure, a main-antenna radiation electrode 51 and a chip antenna
(chip/loop antenna) 52 having a different function are each
connected to a switch 53. The switch 53 is connected to a feeding
point (not illustrated) via a matching circuit. That is, this
antenna structure has a configuration in which the main-antenna
radiation electrode 51 and the chip antenna 52 are selectively
connected to the single feeding point via the switch 53.
SUMMARY
[0005] In an embodiment, an antenna module includes a circuit board
including two feeding parts having different frequencies of feeding
respectively on a first frequency side and a second frequency side
higher than the first frequency side. A first feeding radiation
electrode is connected to the feeding part on the lower frequency
side and performs an antenna operation. A second feeding radiation
electrode is connected to the feeding part on the higher frequency
side and performs an antenna operation. The second feeding
radiation electrode is smaller than the first feeding radiation
electrode, is on the first feeding radiation electrode with an
insulating part therebetween, and has an integrated structure the
first feeding radiation electrode. Unbalanced feeding lines
including a hot line and a ground line are connected to each of the
first and second feeding radiation electrodes. The hot line
connected to each of the first and second feeding radiation
electrodes is connected to a corresponding feeding part, and the
ground line connected to the second feeding radiation electrode is
connected, via the first feeding radiation electrode, to a ground
provided on a side of the circuit board, in such a manner that the
second feeding radiation electrode performs an antenna operation in
which the second feeding radiation electrode and the first feeding
radiation electrode are electrically coupled to each other.
[0006] In a more specific embodiment, the antenna module may
include a circuit having a frequency characteristic exhibiting a
high impedance at an exciting frequency of the second feeding
radiation electrode connected to the ground line connected to the
first feeding radiation electrode, and a circuit having a frequency
characteristic exhibiting a high impedance at an exciting frequency
of the first feeding radiation electrode connected to the ground
line connected to the second feeding radiation electrode.
[0007] In another more specific embodiment, the ground line
connected to the second feeding radiation electrode may be on the
same plane as the first feeding radiation electrode, and the hot
line connected to the second feeding radiation electrode may be
near and forms a coplanar structure with the ground line.
[0008] In another more specific embodiment, the ground line
connected to the second feeding radiation electrode may be formed
by employing the first feeding radiation electrode, and the hot
line may be formed at a rear side of the ground line to provide a
microstrip line structure or a triplate structure.
[0009] In yet another more specific embodiment, the antenna module
may include a chip antenna including the second feeding radiation
electrode on the first feeding radiation electrode, where one end
of the second feeding radiation electrode is connected in a
high-frequency manner to the first feeding radiation electrode,
such that the chip antenna serves as a chip antenna of a
.lamda./4-resonant type.
[0010] In another more specific embodiment, the second feeding
radiation electrode may be formed of a helical electrode having a
helical structure, and the chip antenna including the second
feeding radiation electrode may be provided on the first feeding
radiation electrode.
[0011] In another more specific embodiment, at least one of the
first and second feeding radiation electrodes is connected to a
frequency-variable circuit, and connection lines for controlling
the frequency-variable circuit are near the unbalanced feeding
lines.
[0012] In another more specific embodiment, a matching circuit may
be formed for at least the second feeding radiation electrode, out
of the second feeding radiation electrode and the first feeding
radiation electrode, and the matching circuit for the second
feeding radiation electrode may be on the first feeding radiation
electrode.
[0013] In still another more specific embodiment, the first feeding
radiation electrode or the second feeding radiation electrode may
be provided in a plural form.
BRIEF DESCRIPTION OF DRAWINGS
[0014] FIG. 1a is a schematic explanatory diagram for explaining an
antenna module according to a first exemplary embodiment.
[0015] FIG. 1b is a schematic block explanatory diagram for
explaining the antenna module according to the first exemplary
embodiment.
[0016] FIG. 1c is a schematic block explanatory diagram for
explaining the antenna module according to the first exemplary
embodiment.
[0017] FIG. 2a is an explanatory diagram schematically
illustrating, by using a cross-sectional view and a plan view, an
example of a structure of unbalanced feeding lines.
[0018] FIG. 2b is an explanatory diagram schematically
illustrating, by using a cross-sectional view and a plan view,
another example of a structure of the unbalanced feeding lines.
[0019] FIG. 2c is an explanatory diagram schematically
illustrating, by using a cross-sectional view and a rear view,
another example of a structure of the unbalanced feeding lines.
[0020] FIG. 3a is a schematic explanatory diagram for explaining an
antenna module according to a second exemplary embodiment.
[0021] FIG. 3b is a schematic block explanatory diagram for
explaining the antenna module according to the second exemplary
embodiment.
[0022] FIG. 4 is an explanatory diagram illustrating an example of
a chip antenna.
[0023] FIG. 5 is an explanatory diagram illustrating an example of
a configuration of formation of unbalanced feeding lines and
control lines.
[0024] FIG. 6 is an explanatory diagram illustrating a structure of
a multi-band antenna having a foldable structure of an example of
related art.
[0025] FIG. 7 is an explanatory diagram illustrating the structure
of a multi-band antenna of another example of related art.
DETAILED DESCRIPTION
[0026] The inventor realized that in an antenna element
configuration such as shown in FIG. 6, in which each of the antenna
element 41 and the antenna element 42 is smaller than 1/4 the
wavelength of a free space where the antenna elements 41 and 42
each perform a radiating operation including the casings 48 and 49,
problems can occur. More specifically, because the casing 48 is
determined in advance to have a length in accordance with the
design of a cellular phone, there is a low degree of freedom in
designing of installation, dimensions etc. of the antenna elements
41 and 42. Furthermore, there is a problem in that it is difficult
for radiation of the antenna element 41 and radiation of the
antenna element 42 to have individually optimal characteristics.
Moreover, since the antenna element 41 with a band of 800 MHz and
the antenna element 42 with a band of 1.7/2 GHz are individually
formed and arranged in a limited space, the size of the antenna
element 41 is reduced. This causes a problem of limitation in
increasing the bandwidth of 800 MHz band.
[0027] In the antenna structure illustrated in FIG. 7, the
operation of the main-antenna radiation electrode 51 and the
operation of the chip antenna 52 are selectively performed by the
switch 53. The inventor realized this causes a problem in which the
main-antenna radiation electrode 51 and the chip antenna 52 cannot
be used at the same time. Furthermore, in this antenna structure,
the chip antenna 52 serves as an unbalanced feed chip antenna. Such
an unbalanced feed chip antenna is often designed to be small by
positively employing radiation from a casing, and the
characteristics of such an unbalanced feed chip antenna depend on
the position where the antenna is installed and the size of the
casing in which the antenna is installed. Therefore, there is a
problem in that it is difficult to design the chip antenna 52
optimally.
[0028] Hereinafter, exemplary embodiments of the present disclosure
that address the above problems will now be explained with
reference to the drawings.
[0029] FIG. 1a illustrates a schematic plan view of a structure of
an antenna module according to a first exemplary embodiment. The
antenna module according to the first embodiment is provided in the
casing of a cellular phone. As illustrated in the drawing, two
feeding parts 5 and 6 having different frequencies of feeding are
formed on a circuit board 4 of the casing. A first feeding
radiation electrode 1 is connected to the feeding part 5, which is
on a lower frequency side of the two feeding parts 5 and 6, and
performs an antenna operation. A second feeding radiation electrode
2 is connected to the feeding part 6, which is on a higher
frequency side of the two feeding parts 5 and 6, and performs an
antenna operation. For example, the frequency of feeding on the
lower frequency side can be set to a band of 800 MHz, and the
frequency of feeding on the higher frequency side can be set to a
band of 1.7/2 GHz.
[0030] The second feeding radiation electrode 2 is formed so as to
be smaller than the first feeding radiation electrode 1. The first
feeding radiation electrode 1 and the second feeding radiation
electrode 2 are formed as an integrated structure. A chip antenna 3
including the second feeding radiation electrode 2 is provided on
the first feeding radiation electrode 1. The chip antenna 3 is
formed by arranging the second feeding radiation electrode 2 on an
insulating substrate 8 (or sheet). Accordingly, the second feeding
radiation electrode 2 is configured to be provided on the first
feeding radiation electrode 1 with the insulating part
therebetween. The shape of the second feeding radiation electrode 2
is not necessarily limited to the depicted shape and may be
appropriately set. The second feeding radiation electrode 2 may
have a shape, for example, illustrated in FIG. 1a, or may have a
shape, for example, illustrated in any of FIGS. 2a to 2c. In FIGS.
1b and 1c, the shape of the second feeding radiation electrode 2 is
illustrated in an abbreviated manner.
[0031] For example, in FIG. 2c, one end of the second feeding
radiation electrode 2 is electrically connected in a high-frequency
manner to the first feeding radiation electrode 1. This structure
causes the chip antenna 3 to serve as a chip antenna of a
.lamda.g/4-resonant type (.lamda.g represents a case of wavelength
shortening) at high frequencies. That is, the total electrical
length obtained by adding the electrical length of the first
feeding radiation electrode 1 (here, the length in the longitudinal
direction of the first feeding radiation electrode 1) and the
electrical length of the second feeding radiation electrode 2 is
set to .lamda./2 the electrical length at the exciting frequency of
the second feeding radiation electrode 2, so that radiation is
performed. The antenna operation on the lower frequency side by the
first feeding radiation electrode 1 is independently configured so
as not to affect the second feeding radiation electrode 2.
[0032] The total length obtained by adding the electrical length of
the first feeding radiation electrode 1 and the length l in the
longitudinal direction of the circuit board 4 (see FIG. 1) is set
to be equivalent to .lamda..sub.0/2 the electrical length at the
exciting frequency of the first feeding radiation electrode 1. The
first feeding radiation electrode 1 performs an antenna operation
on a lower frequency side in which the first feeding radiation
electrode 1 and the circuit board 4 each perform a radiating
operation.
[0033] As illustrated in FIG. 1a, hot lines H1 and H2 and ground
lines G1 and G2 are connected to the first feeding radiation
electrode 1 and the second feeding radiation electrode 2,
respectively. The hot line H1 and the ground line G1, which are
connected to the first feeding radiation electrode 1, form
unbalanced feeding lines. Similarly, the hot line H2 and the ground
line G2, which are connected to the second feeding radiation
electrode 2, form unbalanced feeding lines. The hot lines H1 and H2
are connected to the corresponding feeding parts 5 and 6.
[0034] The ground line G1 is connected to the ground (ground
electrode) provided on the side of the circuit board 4 (here, on
the front side). Furthermore, the ground line G2 for the second
feeding radiation electrode 2 is connected, via the first feeding
radiation electrode 1, to the ground provided on the side of the
circuit board 4, so that the second feeding radiation electrode 2
can perform an antenna operation in which the second feeding
radiation electrode 2 and the first feeding radiation electrode 1
are electrically coupled to each other. In the present disclosure,
in a case where the ground of the casing is connected to the ground
of the circuit board, the ground provided on the side of the
circuit board means all the grounds connected to the ground of the
circuit board, for example, including the ground of the casing.
[0035] As illustrated in the schematic block explanatory diagram of
FIG. 1b, a series matching circuit for lower frequency ZSL and
circuit for connecting ground to ground line for lower frequency ZL
are arranged for the unbalanced feeding lines (i.e., the hot line
H1 and the ground line G1) connected to the first feeding radiation
electrode 1. The circuit ZSL is connected to the hot line H1, and
the circuit ZL is connected to the ground line G1. The circuits ZSL
and ZL have a frequency characteristic exhibiting a high impedance
at the exciting frequency of the second feeding radiation electrode
2 and achieve impedance matching at the exciting frequency of the
first feeding radiation electrode 1. A series matching circuit for
higher frequency ZSH and circuit for connecting ground to ground
line for higher frequency ZH are arranged for the unbalanced
feeding lines (i.e., the hot line H2 and the ground line G2)
connected to the second feeding radiation electrode 2. The circuit
ZSH is connected to the hot line H2 and the circuit ZH is connected
to the ground line G2. The circuit ZSH is formed on the first
feeding radiation electrode 1. The circuits ZSH and ZH have a
frequency characteristic exhibiting a high impedance at the
exciting frequency of the first feeding radiation electrode 1 and
achieve impedance matching at the exciting frequency of the second
feeding radiation electrode 2. As illustrated in the schematic
block explanatory diagram of FIG. 1c, the circuits ZSL and ZSH
provided in the embodiment shown in FIG. 1b may be provided in
other embodiments.
[0036] Although the way of forming the unbalanced feeding lines
connected to the second feeding radiation electrode 2 is not
particularly limited, the unbalanced feeding lines can be
configured, for example, as illustrated in FIG. 2a. This
configuration has a coplanar structure in which, out of the ground
line G2 and the hot line H2 connected to the second feeding
radiation electrode 2, the ground line G2 is formed by employing
the first feeding radiation electrode 1 and the hot line H2 is
formed near the ground line G2. In the example illustrated in FIG.
2b, out of the ground line G2 and the hot line H2 connected to the
second feeding radiation electrode 2, the ground line G2 is formed
by employing the first feeding radiation electrode 1. Here, the
first feeding radiation electrode 1 is formed on a rear side, which
is opposite to the side on which the second feeding radiation
electrode 2 is formed. In addition, a configuration including a
microstrip line structure or a triplate structure can be provided
by forming the hot line H2 on a rear side of the ground line G2
(that is, a front side).
[0037] FIG. 3a illustrates, by using a schematic plan view, the
configuration of an antenna module according to a second exemplary
embodiment. In the explanation of the second exemplary embodiment,
parts of the same names as those in the first embodiment are
referred to with the same reference numerals and signs and
redundant explanations of those parts will not be provided or will
be simplified. A feature of the second exemplary embodiment, which
is different from those in the first exemplary embodiment, is that
the first feeding radiation electrode 1 is formed by two electrodes
1a and 1b that are arranged with a space therebetween.
[0038] As illustrated in a schematic block explanatory diagram of
FIG. 3b, the first feeding radiation electrode 1a and the first
feeding radiation electrode 1b are electrically connected to each
other with a balloon circuit (a balance-unbalance conversion
circuit; phase inversion circuit) ZB therebetween. On the first
feeding radiation electrode 1b, the second feeding radiation
electrode 2 and the chip antenna 3 including the second feeding
radiation electrode 2 are provided. In FIGS. 3a and 3b, the shape
of the second feeding radiation electrode 2 is illustrated in an
abbreviated manner.
[0039] The antenna module according to the second exemplary
embodiment can be provided inside a small-sized PC. In the first
exemplary embodiment, a configuration in which the first feeding
radiation electrode 1 resonates in conjunction with the circuit
board 4 is provided. In contrast, in the second exemplary
embodiment, a configuration in which the first feeding radiation
electrode 1a and the first feeding radiation electrode 1b resonate
in conjunction with each other is provided. Therefore, in the
second exemplary embodiment, the characteristic of the first
feeding radiation electrode 1 is determined in accordance with the
total length of the electrical length of the first feeding
radiation electrode 1a and the electrical length of the first
feeding radiation electrode 1b, etc.
[0040] The present disclosure is not limited to the embodiments
described above, and various other embodiments may be employed. For
example, a pattern for forming the second feeding radiation
electrode 2 to be formed in the chip antenna 3 is not particularly
limited and can be set appropriately. For example, as illustrated
in FIG. 4, the second feeding radiation electrode 2 may be formed
of a helical electrode having a helical structure, and the chip
antenna 3 including the second feeding radiation electrode 2 may be
formed on the first feeding radiation electrode 1.
[0041] In addition, at least one of the first and second feeding
radiation electrodes 1 and 2 may be connected to a
frequency-variable circuit, and, for example, as illustrated in
FIG. 5, connection lines 9 for controlling the frequency-variable
circuit may be formed near unbalanced feeding lines.
[0042] Furthermore, although the chip antenna 3 including the
second feeding radiation electrode 2 is provided on the first
feeding radiation electrode 1 in each of the above embodiments, the
second feeding radiation electrode 2 is not necessarily formed in
the form of the chip antenna 3. That is, the second feeding
radiation electrode 2 is only needed to be formed on the first
feeding radiation electrode 1 with an insulating part therebetween
and be electrically connected to the first feeding radiation
electrode 1.
[0043] Furthermore, the details of the shape, size, and so on of
the first feeding radiation electrode 1 and the second feeding
radiation electrode 2 are not particularly limited and can be set
appropriately, for example, in accordance with the size and so on
of a cellular phone or a small-sized PC.
[0044] Furthermore, regarding the antenna module according to the
first exemplary embodiment, implementation in the casing has been
explained by taking an example of a wireless device having a
foldable structure. However, a wireless device in which the antenna
module is to be implemented does not necessarily have a foldable
structure and can be applied to a general straight terminal or a
slide structure. Moreover, the position at which the antenna module
is to be implemented is not limited.
[0045] The antenna module according to the present disclosure is
capable of achieving the compatibility of radiation characteristics
of two feeding radiation electrodes having different exciting
frequencies, and such antennas can be used at the same time
according to need. Thus, the antenna module can be used as an
antenna module for a wireless device, such as a cellular phone or a
small-sized PC.
[0046] In embodiments according to the present disclosure, an
antenna module is provided with first and second feeding radiation
electrodes, where each of these electrodes is connected to one of
two feeding parts having different frequencies of feeding and
performing an antenna operation. The ground for the second feeding
radiation electrode that performs an antenna operation on a higher
frequency side is connected, doubling as the first feeding
radiation electrode. The first feeding radiation electrode is
configured to serve as one electrode that also performs an
unbalanced antenna operation of the second feeding radiation
electrode so that the first and second feeding radiation electrodes
can perform, in conjunction with each other, an asymmetric dipole
antenna operation. Therefore, the characteristics of the second
feeding radiation electrode are not likely to be susceptible to the
size of a circuit board side (including a casing connected to the
circuit board).
[0047] Consequently, in embodiments consistent with the present
disclosure, it is possible to design the first and second feeding
radiation electrodes optimally, and excellent radiation
characteristics of the first and second feeding radiation
electrodes can be achieved. In addition, an antenna operation is
not performed by selectively connecting, using a switch, the first
and second feeding radiation electrodes to a single feeding part.
Thus, since isolation of individual frequencies can be readily
controlled, the first feeding radiation electrode and the second
feeding radiation electrode can be used at the same time.
[0048] In addition, the small-sized second feeding radiation
electrode is provided on the first feeding radiation electrode with
the insulating part therebetween. Thus, unlike a case where the
first feeding radiation electrode and the second feeding radiation
electrode are independently provided on the circuit board, there is
no need to require a space where the second feeding radiation
electrode is to be arranged, separately from a space where the
first feeding radiation electrode is to be arranged. Therefore,
even in a limited antenna space in a cellular phone or the like, a
sufficient space can be provided for the arrangement of the first
and second feeding radiation electrodes, and the electrical length
of first and second feeding radiation electrodes can be set to be
sufficiently long.
[0049] Furthermore, a hot line and a ground line are connected to
each of the first feeding radiation electrode and the second
feeding radiation electrode. The hot line is connected to a
corresponding feeding part, and the ground line is connected to the
ground provided on a side of the circuit board. Since a circuit
having a frequency characteristic exhibiting a high impedance at
the exciting frequency of an opposite feeding radiation electrode
is arranged for each ground line, the radiation characteristics of
the first and second feeding radiation electrodes can be adjusted
to be optimal in an independent manner. Thus, an antenna module can
be designed adequately. That is, in the present disclosure, the
first feeding radiation electrode is not deteriorated by the second
feeding radiation electrode, and the second feeding radiation
electrode also achieves an optimal resonant characteristic.
[0050] According to an above-described embodiment of the present
disclosure, out of the ground line and the hot line connected to
the second feeding radiation electrode, the ground line is formed
by employing the first feeding radiation electrode, and the hot
line is formed near the ground line, so that a coplanar structure
is provided. With this structure, the thickness of an area where
the ground line and the hot line are formed can be reduced.
[0051] In addition, according to another preferable embodiment, out
of the ground line and the hot line connected to the second feeding
radiation electrode, the ground line is formed by employing the
first feeding radiation electrode, and the hot line is formed at a
rear side of the ground line. Accordingly, a microstrip line
structure or a triplate structure can be provided. Thus,
unnecessary radiation from the unbalanced feeding lines of the
second feeding radiation electrode can be suppressed.
[0052] Furthermore, according to another embodiment, a chip antenna
including the second feeding radiation electrode is provided on the
first feeding radiation electrode, and one end of the second
feeding radiation electrode is connected in a high-frequency manner
to the first feeding radiation electrode, so that the chip antenna
serves as a chip antenna of a .lamda./4-resonant type. Thus, since
the current distribution of the first feeding radiation electrode
can be controlled by the second feeding radiation electrode, the
first feeding radiation electrode is unlikely to be susceptible to
metal such as the ground on a side of the circuit board (including
metal on a casing side in which the circuit board is arranged).
[0053] Furthermore, according to another embodiment, the second
feeding radiation electrode can be formed of a helical electrode
having a helical structure, and the chip antenna including the
second feeding radiation electrode can be provided on the first
feeding radiation electrode. Thus, the electrical length of the
second feeding radiation electrode can be easily formed to be
loner, and the bandwidth of the antenna can be increased.
[0054] In the present disclosure, regarding the second feeding
radiation electrode, not limited to the chip antenna, a small-sized
antenna having the same function can be integrated with the first
feeding radiation electrode.
[0055] In addition, according to another embodiment, at least one
of the first and second feeding radiation electrodes can be
connected to a frequency-variable circuit, and connection lines for
controlling the frequency-variable circuit can be formed near the
unbalanced feeding lines. Thus, the density of integration of the
antenna module can be increased.
[0056] Furthermore, according to another embodiment, a matching
circuit can be formed for at least the second feeding radiation
electrode, out of the second feeding radiation electrode and the
first feeding radiation electrode, and the matching circuit for the
second feeding radiation electrode can be formed on the first
feeding radiation electrode. Thus, a high-frequency current that
flows to the first feeding radiation electrode and serves as an
image current of the second feeding radiation electrode can be
easily controlled, and matching can be easily achieved.
[0057] Furthermore, according to another embodiment, the first
feeding radiation electrode or the second feeding radiation
electrode can be provided in a plural form. Thus, in a case where a
plurality of bandwidths are further required in a portable device
for which multi-band processing is required, the size of the
antenna module can be reduced.
* * * * *